Hi Miklos,
I was considering the "FIXME: workdir is not needed for a R/O mount"
you left in ovl_fill_super() these days.
Actually Seunghun (Seunghun Lee <way...@gmail.com>) has sent a patch
about these problem. But I have some different ideas. I think there are
two ways to fix this problem. One, just remove this *FIXME*. Another,
Allow non-workdir mount.
1) Remove *FIXME*; Further, use workdir in R/W case only
As multi-layer mount are allowed in ovl, users could initialize a R/O
mount by setting multi lower directories. Workdir should only be used
in R/W case with upperdir exist. So this *FIXME* can be removed.
We should add some information in the code and document about this.
2) Allow non-workdir mount
This logic is simple, just mark upper_mnt as R/O if workdir is not exist
in the option line.
I've written a patch about it below. But I'm not sure which way is
better, or there are other acceptable solutions. I need your advisement.
Here is a problem, if upper partition is R/O mount, ovl can't create
*work* directory in workdir and return an error:
overlayfs: failed to create directory ./workdir/work
I guess this problem can be fixed if we decide how to deal with R/O
mount.
Thanks,
Hu
Non-workdir mount patch:
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index b90952f..c7141ff 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -520,7 +520,8 @@ static int ovl_show_options(struct seq_file *m, struct
dentry *dentry)
seq_printf(m, ",lowerdir=%s", ufs->config.lowerdir);
if (ufs->config.upperdir) {
seq_printf(m, ",upperdir=%s", ufs->config.upperdir);
- seq_printf(m, ",workdir=%s", ufs->config.workdir);
+ if (ufs->config.workdir)
+ seq_printf(m, ",workdir=%s", ufs->config.workdir);
}
return 0;
}
@@ -530,7 +531,8 @@ static int ovl_remount(struct super_block *sb, int *flags,
char *data)
struct ovl_fs *ufs = sb->s_fs_info;
if (!(*flags & MS_RDONLY) &&
- (!ufs->upper_mnt || (ufs->upper_mnt->mnt_sb->s_flags & MS_RDONLY)))
+ (!ufs->upper_mnt || !ufs->workdir ||
+ (ufs->upper_mnt->mnt_sb->s_flags & MS_RDONLY)))
return -EROFS;
return 0;
@@ -837,28 +839,24 @@ static int ovl_fill_super(struct super_block *sb, void
*data, int silent)
sb->s_stack_depth = 0;
if (ufs->config.upperdir) {
- /* FIXME: workdir is not needed for a R/O mount */
- if (!ufs->config.workdir) {
- pr_err("overlayfs: missing 'workdir'\n");
- goto out_free_config;
- }
-
err = ovl_mount_dir(ufs->config.upperdir, &upperpath);
if (err)
goto out_free_config;
- err = ovl_mount_dir(ufs->config.workdir, &workpath);
- if (err)
- goto out_put_upperpath;
+ if (ufs->config.workdir) {
+ err = ovl_mount_dir(ufs->config.workdir, &workpath);
+ if (err)
+ goto out_put_upperpath;
- err = -EINVAL;
- if (upperpath.mnt != workpath.mnt) {
- pr_err("overlayfs: workdir and upperdir must reside
under the same mount\n");
- goto out_put_workpath;
- }
- if (!ovl_workdir_ok(workpath.dentry, upperpath.dentry)) {
- pr_err("overlayfs: workdir and upperdir must be
separate subtrees\n");
- goto out_put_workpath;
+ err = -EINVAL;
+ if (upperpath.mnt != workpath.mnt) {
+ pr_err("overlayfs: workdir and upperdir must
reside under the same mount\n");
+ goto out_put_workpath;
+ }
+ if (!ovl_workdir_ok(workpath.dentry, upperpath.dentry))
{
+ pr_err("overlayfs: workdir and upperdir must be
separate subtrees\n");
+ goto out_put_workpath;
+ }
}
sb->s_stack_depth = upperpath.mnt->mnt_sb->s_stack_depth;
}
@@ -901,12 +899,16 @@ static int ovl_fill_super(struct super_block *sb, void
*data, int silent)
goto out_put_lowerpath;
}
- ufs->workdir = ovl_workdir_create(ufs->upper_mnt,
workpath.dentry);
- err = PTR_ERR(ufs->workdir);
- if (IS_ERR(ufs->workdir)) {
- pr_err("overlayfs: failed to create directory %s/%s\n",
- ufs->config.workdir, OVL_WORKDIR_NAME);
- goto out_put_upper_mnt;
+ if (ufs->config.workdir) {
+ ufs->workdir = ovl_workdir_create(ufs->upper_mnt,
workpath.dentry);
+ err = PTR_ERR(ufs->workdir);
+ if (IS_ERR(ufs->workdir)) {
+ pr_err("overlayfs: failed to create directory
%s/%s\n",
+ ufs->config.workdir, OVL_WORKDIR_NAME);
+ goto out_put_upper_mnt;
+ }
+ } else {
+ ufs->upper_mnt->mnt_flags |= MNT_READONLY;
}
}
@@ -932,8 +934,12 @@ static int ovl_fill_super(struct super_block *sb, void
*data, int silent)
ufs->numlower++;
}
- /* If the upper fs is r/o or nonexistent, we mark overlayfs r/o too */
- if (!ufs->upper_mnt || (ufs->upper_mnt->mnt_sb->s_flags & MS_RDONLY))
+ /*
+ * If the upper fs is r/o or nonexistent, or workdir is absent,
+ * we mark overlayfs r/o too
+ */
+ if (!ufs->upper_mnt || !ufs->workdir ||
+ (ufs->upper_mnt->mnt_sb->s_flags & MS_RDONLY))
sb->s_flags |= MS_RDONLY;
sb->s_d_op = &ovl_dentry_operations;
--
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